This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Swedish Application No. 0101837-3 filed on May 23, 2001, the entire content of which is incorporated herein by reference.
This invention generally relates to continuous casting machine. More particularly, the invention pertains to a method for detecting a seized or still standing roller in a continuous casting machine.
A continuous casting machine produces steel material from molten steel. The steel material can be used for example as a starting material in rolling processes for producing sheet metal to be used in, for instance, vehicles.
In the continuous casting machine, molten steel flows from a ladle and down in a tundish from which it is transported further down into a mold. In the mold, which is water-cooled, the slab of continuous cast material begins to form a solid shell. Then, the slab is continuously transported along a curved track by a large number of rollers arranged in segments which continue to shape and cool the slab to the final thickness of the steel material. At the end of the track, the material is cut into suitable pieces.
The rollers of the continuous casting machine are rotatably mounted with their axes substantially perpendicular to the longitudinal extension or longitudinal extent of the curved track. To lead and support the slab of continuous cast material, the rollers are arranged in pairs, with each pair comprising an upper roller and a lower roller.
Further, the rollers are rotatably mounted in supporting members at each end of the rollers. Due to the length of the rollers, and thus the load on the rollers, the rollers are generally split into roller portions. The roller portions are either independently mounted in supporting members or nonrotatably provided on a common shaft, with the shaft being mounted in supporting members. The supporting members can be, for example, rolling bearings or sliding bearings. Further, the supporting member also comprises a suitable bearing housing.
During transportation of the slab along the track, each roller is supposed to rotate at a speed appropriate for providing the slab with an even conveyance without unnecessary stresses or surface wear. However, one of the rollers or several of the rollers can stop or start to seize.
Stopping or seizing of the rollers can derive from several factors. Examples include supporting member failures due to, for example, starvation of lubricant, particles blocking the supporting member or deformation of the rolling elements in a rolling bearing. A further factor is slag and dirt from the cooling water that has been deposited on the frame of the machine or on the rollers. This slag can disturb the function of the machine.
When one roller or several rollers stop or begin to seize, the material will be negatively effected. For example, scratches are very likely to appear on the slab surface. These scratches can of course be treated by, for instance, grinding or remelting the surface layer. However, any treatment of the material after the casting process necessarily beings about an increase in costs.
In the beginning of the process where the solidified layer is thin, a more serious problem can occur. This is referred to as a xe2x80x9cbreak outxe2x80x9d. During a break out, the slab is badly damaged as the solidified surface layer is torn open so that the inner molten material is able to flow out.
It would thus be desirable to detect the stoppage or seizure of rollers that cause scratches and/or break outs to the material being cast to avoid the need for costly treatment of the material after the casting process.
According to one aspect, a method is provided for detecting a seized or still standing roller in a track of rollers in a continuous casting machine, with each roller being rotatably mounted in supporting members and arranged with its axis substantially perpendicular to a longitudinal extent of the track, and with the rollers being arranged for transporting elongated material produced in the continuous casting machine. The method includes measuring a load, which is substantially parallel with a direction of extent of the track, exerted on at least one supporting member of each roller, and establishing the existence of a seized or still standing roller when the measured load deviates from a predetermined value by virtue of a force induced on the roller by seizure or stoppage of the roller at contact with the elongated material.
According to another aspect, a method for detecting a seized or still standing roller in a continuous casting machine comprises transporting elongated material produced in the continuous casting machine along a track of rollers each rotatably mounted in supporting members and having an axis arranged substantially perpendicular to a longitudinal extent of the track, measuring a load in a direction along the direction of extent of the track that is exerted on at least one supporting member of a plurality of the rollers, comparing the measured load exerted on the at least one supporting member of each of the plurality of rollers to a predetermined value, and determining that at least one of the plurality of rollers is seized or is a still standing roller when the measured load in the at least one supporting member of the at least one of the plurality of rollers deviates from the predetermined value.